Method of manufacturing superconducting wire

ABSTRACT

A method of manufacturing a superconducting wire includes the step of drawing a wire formed by coating raw material powder for a superconductor with a metal or a wire with a multifilamentary structure, the step of sealing an end portion of a clad wire or a multifilamentary wire after the step of drawing, and the step of first rolling, rolling the multifilamentary wire after the step of sealing. With this method, a superconducting wire having high and uniform performance can be obtained.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

Japanese Priority Application 2004-183634, filed Jun. 6, 2004 includingthe specification, drawings, claims and abstract, is incorporated hereinby reference in its entirety. This application is a U.S. National Stageof Application PCT/JP2005/002412 filed Feb. 17, 2005, incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method of manufacturing asuperconducting wire, and in particular, to a method of manufacturing asuperconducting wire capable of obtaining a superconducting wire withhigh and uniform performance.

BACKGROUND ART

A superconducting wire made of a multifilamentary wire formed by coatingan oxide superconductor having for example Bi2223 phase with a metal isconventionally expected to be applied to a superconducting cable and amagnet, since it can be used at a temperature cooled by liquid nitrogenand a relatively high critical current density can be obtained, and itcan be prolonged relatively easily.

Such a superconducting wire has been manufactured as will be describedbelow. Firstly, a wire is fabricated to have a form in which rawmaterial powder for a superconductor containing such as Bi2223 phase iscoated with a metal. Next, by performing thermal treatment and rollingrepeatedly, a superconducting phase is generated as aligned to asuperconducting filament part of the wire, and thus a tape-likesuperconducting wire is obtained. Such a method of manufacturing asuperconducting wire is disclosed for example in Japanese Patent No.2636049 (Japanese Patent Laying-Open No. 03-138820) (Patent Document 1)and Japanese Patent No. 2855869 (Japanese Patent Laying-Open No.04-292812) (Patent Document 2).

-   Patent Document 1: Japanese Patent No. 2636049 (Japanese Patent    Laying-Open No. 03-138820)-   Patent Document 2: Japanese Patent No. 2855869 (Japanese Patent    Laying-Open No. 04-292812)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Conventionally, an optimum manufacturing condition for eachmanufacturing step has been sought to improve performance (such as acritical current value) of a superconducting wire. However, even when asuperconducting wire is manufactured under the same optimum condition,the obtained superconducting wire has variations in each performance.Further, some of the obtained superconducting wire has poor performance,and thus a high performance superconducting wire cannot be obtained.

Therefore, an object of the present invention is to provide a method ofmanufacturing a superconducting wire capable of obtaining asuperconducting wire with high and uniform performance.

Means to Solve the Problems

A method of manufacturing a superconducting wire in an aspect of thepresent invention includes the steps of drawing a wire formed by coatingraw material powder for a superconductor with a metal, sealing an endportion of the wire after the step of drawing, and rolling the wireafter the step of sealing.

After careful examination, inventors of the present invention have foundthat the obtained superconducting wire has variations in eachperformance due to reasons which will be described below. In an intervalbetween the step of drawing and the step of rolling, CO₂ (carbondioxide), H₂O (water), O₂ (oxygen) and the like in the air intrude intothe wire through an end portion of the wire not coated with a metal.This leads to generation of a hetero phase other than thesuperconducting phase during sintering, or an uneven thickness of thewire. In particular, as for the thickness, there occurs a phenomenonthat the wire has a considerably increased thickness at its end portion.The generation of a hetero phase during sintering interferes with thegeneration of the superconducting phase, and deterioratessuperconducting properties such as the critical current value. Further,if the wire has an uneven thickness, pressure is not uniformly appliedto the wire when rolling is performed later, and thus the obtainedsuperconducting wire has an uneven thickness. As a result, theperformance of the superconducting wire is deteriorated. Conventionally,no treatment has been performed in the interval between the step ofdrawing and the step of rolling, and thus the obtained superconductingwire has variations in each performance depending on the difference inthe condition for holding each piece of the wire between the step ofdrawing and the step of rolling.

Consequently, by sealing the end portion of the wire in the intervalbetween the step of drawing and the step of rolling, CO₂, H₂O, and O₂ inthe air are less likely to intrude into raw material powder through theend portion of the wire. As a result, a hetero phase is less likely tobe generated during sintering and the wire has a uniform thickness, andthus a superconducting wire having high and uniform performance can beobtained.

A method of manufacturing a superconducting wire in another aspect ofthe present invention includes the steps of drawing a wire formed bycoating raw material powder for a superconductor with a metal n times (nis an integer satisfying n≧2), and rolling the wire after the step ofdrawing the wire n times. The method further includes the step ofsealing an end portion of the wire in at least one of an intervalbetween the step of k-th (k is an integer satisfying n−1≧k≧1) drawing inthe step of drawing the wire n times and the step of (k+1)-th drawing inthe step of drawing the wire n times and an interval between the step ofn-th drawing in the step of drawing the wire n times and the step ofrolling.

After careful examination, the inventors of the present invention havefound that the obtained superconducting wire has variations in eachperformance due to reasons which will be described below. When the stepof drawing the wire n times is performed to manufacture asuperconducting wire, CO₂ (carbon dioxide), H₂O (water), O₂ (oxygen) andthe like in the air intrude into the wire through an end portion of thewire not coated with a metal, in each interval between the steps ofdrawing from the step of first drawing to the step of n-th drawing, andin an interval between the step of the n-th drawing and the step ofrolling. This leads to generation of a hetero phase other than thesuperconducting phase during sintering, or an uneven thickness of thewire. In particular, as for the thickness, there occurs a phenomenonthat the wire has a considerably increased thickness at its end portion.The generation of a hetero phase during sintering interferes with thegeneration of the superconducting phase, and deterioratessuperconducting properties such as the critical current value. Further,if the wire has an uneven thickness, pressure is not uniformly appliedto the wire when rolling is performed later, and thus the obtainedsuperconducting wire has an uneven thickness. As a result, theperformance of the superconducting wire is deteriorated. Conventionally,no treatment has been performed in each interval between the steps ofdrawing from the step of the first drawing to the step of the n-thdrawing, and in the interval between the step of the n-th drawing andthe step of rolling. Accordingly, the obtained superconducting wire hasvariations in each performance depending on the difference in thecondition for holding each piece of the wire in each interval betweenthe steps of drawing from the step of the first drawing to the step ofthe n-th drawing, and in the interval between the step of the n-thdrawing and the step of rolling.

Consequently, by sealing the end portion of the wire in at least one ofeach interval between the steps of drawing from the step of the firstdrawing to the step of the n-th drawing and the interval between thestep of the n-th drawing and the step of rolling, CO₂, H₂O, and O₂ inthe air are less likely to intrude into the raw material powder throughthe end portion of the wire. As a result, a hetero phase is less likelyto be generated during sintering and the wire has a uniform thickness,and thus a superconducting wire having high and uniform performance canbe obtained.

Preferably, in the method of manufacturing a superconducting wire of thepresent invention, the end portion of the wire is sealed with a metal inthe step of sealing.

Thereby, CO₂, H₂O, and O₂ in the air are further less likely to intrudeinto the raw material powder through the end portion of the wire.

Preferably, in the method of manufacturing a superconducting wire of thepresent invention, the metal used for sealing contains at least oneelement selected from the group consisting of silver, lead, tin, copper,and aluminum.

Since these materials have high ductility and mechanical strength, theycan easily be processed when sealing the end portion of the wire, andthey can stably seal the end portion of the wire.

It is to be noted that “sealing” in the present specification refers totreatment for preventing contact between the raw material powder insidethe wire and outside air.

Effects of the Invention

According to the method of manufacturing a superconducting wire of thepresent invention, by sealing the end portion of the wire in theinterval between the step of drawing and the step of rolling, CO₂, H₂O,and O₂ in the air are less likely to intrude into the raw materialpowder through the end portion of the wire. As a result, a hetero phaseis less likely to be generated during sintering and the wire has auniform thickness, and thus a superconducting wire having high anduniform performance can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary sectional perspective view illustrating astructure of a superconducting wire on a conceptual basis.

FIG. 2 is a flow chart illustrating a method of manufacturing asuperconducting wire in a first embodiment of the present invention.

FIG. 3 is a first view illustrating a step in FIG. 2.

FIG. 4 is a second view illustrating a step in FIG. 2.

FIG. 5 is a third view illustrating a step in FIG. 2.

FIG. 6 is a fourth view illustrating a step in FIG. 2.

FIG. 7 is a fifth view illustrating a step in FIG. 2.

FIG. 8 is a sixth view illustrating a step in FIG. 2.

DESCRIPTION OF REFERENCE CHARACTERS

-   1. superconducting wire (multifilamentary wire), 1 a. wire, 1 b.    clad wire, 1 c. multifilamentary wire, 2. superconductor filament, 2    a. raw material powder, 3. sheath part, 3 a, 3 b. pipe, 20 a, 20 b.    sealing member.

Best Modes for Carrying Out the Invention

In the following, an embodiment of the present invention will bedescribed with reference to the drawings.

First Embodiment

FIG. 1 is a fragmentary sectional perspective view illustrating astructure of a superconducting wire on a conceptual basis. Referring toFIG. 1, explanation will be given on for example a multifilamentarysuperconducting wire. A superconducting wire 1 has a plurality ofsuperconductor filaments 2 extending in a longitudinal direction and asheath part 3 coating them. Each of the plurality of superconductorfilaments 2 is made of a material having composition of for example theBi—Pb—Sr—Ca—Cu—O system, and in particular, the optimum material is amaterial containing Bi2223 phase in which an atomic ratio of (bismuthand lead):strontium:calcium:copper is approximately represented by2:2:2:3. Sheath part 3 is made of a material such as silver.

It is to be noted that, although explanation has been given on amultifilamentary wire, an oxide superconducting wire having amonofilamentary structure, in which a single superconductor filament 2is coated with sheath part 3, may be used.

Next, a method of manufacturing the oxide superconducting wire describedabove will be explained.

FIG. 2 is a flow chart illustrating a method of manufacturing asuperconducting wire in a first embodiment of the present invention.FIGS. 3 to 8 illustrate respective steps in FIG. 2.

Referring to FIG. 2, the Powder-In-Tube method is used to manufacture asuperconducting wire with for example the Bi2223 phase. Firstly, forexample five kinds of raw material powder (Bi₂O₃, PbO, SrCO₃, CaCO₃,CuO) are mixed to produce raw material powder in an intermediate state(precursor powder) which will ultimately be changed to a superconductorwith the Bi2223 phase by a reaction caused by thermal treatment (StepS1).

Next, as shown in FIGS. 2 and 3, this raw material powder 2 a is filledinto a pipe 3 a (Step S2). Pipe 3 a is made of a metal such as silver,having an outer diameter of φ10 to 50 mm and a wall thickness of about 3to 15% of the outer diameter. Thereby, a wire 1 a in which raw materialpowder 2 a for the superconductor is coated with pipe 3 a is obtained.Thereafter, degassing of the content of pipe 3 a is performed, and bothends of pipe 3 a are sealed.

Next, as shown in FIGS. 2 and 4, wire 1 a is drawn to form amonofilamentary clad wire 1 b in which the precursor as a filamentarymaterial is coated with a metal such as silver (Step S3). Clad wire 1 bhas a shape of a hexagon with a length between opposite sides of such as2 to 10 mm.

Next, as shown in FIGS. 2 and 5, both end portions of clad wire 1 b aresealed with sealing members 20 a and 20 b (Step S4). The sealing of cladwire 1 b may be performed for example by putting caps made of Teflon(trademark) over the both end portions of clad wire 1 b, or by solderinga metal such as silver to the both end portions of clad wire 1 b. Thatis, it is only necessary to cover the both end portions of clad wire 1 bwith some material. A preferable material for sealing clad wire 1 b is ametal, and in particular, metals such as silver, a silver alloy, lead,tin, copper, and aluminum having ductility and mechanical strengthalmost similar to those of silver are particularly preferable.

Next, as shown in FIGS. 2 and 6, a plurality of clad wires lb arebundled to be fit into a pipe 3 b made of a metal such as silver(multifilamentary fit: Step S5). This pipe 3 b is made of a metal suchas silver or an alloy thereof, having an outer diameter of φ10 to 50 mmand a wall thickness of about 3 to 15% of the outer diameter. Thereby, awire with a multifilamentary structure having a plurality of filamentsmade of raw material powder 2 a is obtained.

Next, as shown in FIGS. 2 and 7, the wire with the multifilamentarystructure in which a plurality of filaments made of raw material powder2 a are coated with sheath part 3 b is drawn to form a multifilamentarywire 1 c in which raw material powder 2 a is embedded within sheath part3 b made of such as silver (Step S6).

Next, as shown in FIGS. 2 and 5, both end portions of multifilamentarywire 1 c are sealed with sealing members 20 a and 20 b (Step S7). Thesealing of multifilamentary wire 1 c may be performed for example byputting caps made of Teflon (trademark) over the both end portions ofmultifilamentary wire 1 c, or by soldering a metal such as silver to theboth end portions of multifilamentary wire 1 c. That is, it is onlynecessary to cover the both end portions of multifilamentary wire 1 cwith some material. A preferable material for sealing multifilamentarywire 1 c is a metal, and in particular, metals such as silver, a silveralloy, lead, tin, copper, and aluminum having ductility and mechanicalstrength almost similar to those of silver are particularly preferable.

Next, as shown in FIGS. 2 and 8, first rolling is performed onmultifilamentary wire 1 c to obtain tape-like multifilamentary wire 1(Step S8). The first rolling is performed at a draft of for example 70to 90%.

Next, tape-like multifilamentary wire 1 is heated to a temperature offor example 800 to 900° C. and held at that temperature for 10 to 200hours, and thus multifilamentary wire 1 is subjected to first sintering(Step S9). Thereby, raw material powder 2 a chemically reacts to becomesuperconductor filament 2.

Next, as shown in FIGS. 2 and 8, multifilamentary wire 1 is subjected tosecond rolling (Step S10). The second rolling is performed at a draft offor example 0 to 20%.

Next, multifilamentary wire 1 is heated to a temperature of 800 to 900°C. under a pressurized atmosphere and held at that temperature for 10 to200 hours, and thus multifilamentary wire 1 is subjected to secondsintering (Step S11). Although the superconducting wire of the presentembodiment is obtained through the steps described above, furtherrolling and sintering may be performed repeatedly after the secondsintering, and the second rolling and the second sintering describedabove may be omitted.

The method of manufacturing a superconducting wire of the presentembodiment includes the step of drawing wire 1 a formed by coating rawmaterial powder 2 a for a superconductor with a metal or a wire with amultifilamentary structure (Step S3, Step S6), the step of sealing anend portion of clad wire 1 b or multifilamentary wire 1 c after the stepof drawing (Step S3, Step S6) (Step S4, Step S7), and the step of thefirst rolling (Step S8) rolling multifilamentary wire 1 c after the stepof sealing (Step S4, Step S7).

According to the method of manufacturing a superconducting wire of thepresent embodiment, by sealing the end portion of clad wire 1 b ormultifilamentary wire 1 c in an interval between the step of drawing(Step S3, Step S6) and the step of the first rolling (Step S8), CO₂, H₂Oand O₂ in the air are less likely to intrude into raw material powder 2a through the end portion of clad wire 1 b or multifilamentary wire 1 c.As a result, a hetero phase is less likely to be generated duringsintering and the wire has a uniform thickness, and thus asuperconducting wire having high and uniform performance can beobtained.

In the method of manufacturing a superconducting wire of the presentembodiment, the end portion of clad wire 1 b or multifilamentary wire 1c is sealed with a metal in the step of sealing (Step S4, Step S7).

Thereby, CO₂, H₂O, and O₂ in the air are further less likely to intrudeinto raw material powder 2 a through the end portion of clad wire 1 b ormultifilamentary wire 1 c.

In the method of manufacturing a superconducting wire of the presentembodiment, the metal used for sealing contains at least one elementselected from the group consisting of silver, lead, tin, copper, andaluminum.

Since these materials have high ductility and mechanical strength, theycan easily be processed when sealing the end portion of clad wire 1 b ormultifilamentary wire 1 c, and they can stably seal the end portion ofclad wire 1 b or multifilamentary wire 1 c.

Although the present embodiment has been described for the case wherethe step of sealing (Step S4, Step S7) is performed after the formationof clad wire 1 b (Step S3) and also after the formation ofmultifilamentary wire 1 c (Step S6), the present invention is notlimited to such a case, and it is sufficient if the step of sealing isperformed between the step of drawing and the step of rolling.

Second Embodiment

Referring to FIGS. 2 and 5, the first embodiment has been described forthe case where wire la is drawn once in the step of drawing (Step S3).In the drawing process, however, it is common that wire 1 a is drawn ntimes (n is an integer satisfying n≧2) consecutively and the diameter ofwire 1 a is gradually decreased to form clad wire 1 b. In the presentembodiment, when wire la is drawn n times, both end portions of wire 1 aor clad wire 1 b are sealed with sealing members 20 a and 20 b in eachinterval between the steps of drawing n times or after the formation ofclad wire 1 b (Step S4).

Further, the first embodiment has been described for the case where awire with a multifilamentary structure is drawn once in the step ofdrawing (Step S6). In the drawing process, however, it is common thatthe wire with a multifilamentary structure is drawn n timesconsecutively and the diameter of the wire with a multifilamentarystructure is gradually decreased to form multifilamentary wire 1 c. Inthe present embodiment, when the wire with a multifilamentary structureis drawn n times, both end portions of the wire with a multifilamentarystructure or multifilamentary wire 1 c are sealed with sealing members20 a and 20 b in each interval between the steps of drawing n times orafter the formation of multifilamentary wire 1 c (Step S7).

It is to be noted that, except for the points described above, themethod of manufacturing the superconducting wire is almost similar tothat in the first embodiment shown in FIGS. 1 to 8, and thus thedescription thereof will not be repeated.

The method of manufacturing a superconducting wire of the presentembodiment includes the step of drawing wire 1 a formed by coating rawmaterial powder 2 a for a superconductor with a metal or a wire with amultifilamentary structure n times (Step S3, Step S6), and the step ofthe first rolling (Step S8) rolling multifilamentary wire 1 c after thestep of drawing n times (Step S3, Step S6). The method further includesthe step of sealing an end portion of wire 1 a, clad wire 1 b, the wirewith a multifilamentary structure, or multifilamentary wire 1 c in atleast one of each interval between the steps of drawing n times (StepS3, Step S6) and an interval between the step of the n-th drawing andthe step of the first rolling (Step S8) (Step S4, Step S7).

According to the method of manufacturing a superconducting wire in thepresent embodiment, by sealing the end portion of wire 1 a, clad wire 1b, the wire with a multifilamentary structure, or multifilamentary wire1 c in each interval between the steps of drawing (Step S3, Step S6) andthe interval between the step of the n-th drawing and the step of thefirst rolling (Step S8), CO₂, H₂O and O₂ in the air are less likely tointrude into raw material powder 2 a through the end portion of wire 1a, clad wire 1 b, the wire with a multifilamentary structure, ormultifilamentary wire 1 c. As a result, a hetero phase is less likely tobe generated during sintering and the wire has a uniform thickness, andthus a superconducting wire having high and uniform performance can beobtained.

It is to be noted that, although explanation has been given in the firstand the second embodiments on the method of manufacturing a bismuth-typemultifilamentary oxide superconducting wire having the Bi2223 phase, thepresent invention is also applicable to a method of manufacturing anoxide superconducting wire having composition other than bismuth-type,such as yttrium-type. In addition, the present invention is alsoapplicable to a method of manufacturing a monofilamentarysuperconducting wire.

Further, although the first and the second embodiments have beendescribed for the case where the second rolling (Step S10) and thesecond sintering (Step S11) are performed after the first sintering(Step S9), these steps may be omitted, and a superconducting wire may becompleted after the first sintering (Step S9).

EXAMPLE

In the following, an example of the present invention will be described.

In the present example, an effect of sealing both end portions ofmultifilamentary wire 1 c in the interval between the step of drawing(Step S6) and the step of the first rolling (Step S8) was examined.Specifically, raw material powder 2 a having the Bi2223 phase wasproduced (Step S1), and thereafter raw material powder 2 a was filledinto pipe 3 a (Step S2) to form wire 1 a. Next, wire 1 a was drawn toform clad wire 1 b (Step S3), and a plurality of clad wire 1 b werebundled without being sealed at both end portions and fit into pipe 3 b(Step S5) to form multifilamentary wire 1 c. Next, multifilamentary wire1 c was drawn (Step S6). In the drawing process, multifilamentary wire 1c was drawn 20 times repeatedly, and its diameter was graduallydecreased to form multifilamentary wire 1 c having a desired diameter.In the present example, when multifilamentary wire 1 c was drawn,samples 1 to 3 were subjected to different treatments. Specifically, asfor sample 1, both end portions of multifilamentary wire 1 c were sealedwith silver solder (Step S7) after the first drawing in the 20-timedrawing. Then, multifilamentary wire 1 c was repeatedly drawn for theremaining 19 times with its both end portions sealed, and thereafterheld for one month. As for sample 2, multifilamentary wire 1 c was drawn20 times repeatedly, and thereafter its both end portions were sealedwith silver solder (Step S7) and it was held for one month. Further, asfor sample 3, multifilamentary wire 1 c was drawn 20 times repeatedlywithout its both end portions sealed, and thereafter it was held for onemonth. Next, the first rolling was performed on multifilamentary wire 1c (Step S8) to obtain tape-like multifilamentary wire 1. Next, the firstsintering was performed on multifilamentary wire 1 (Step S9), andthereafter multifilamentary wire 1 was examined on whether there was anincrease in thickness. Next, the second rolling was performed onmultifilamentary wire 1 (Step S10), and then the second sintering wasperformed (Step S11) to obtain superconducting wire 1 having a length of400 m and a silver ratio (a ratio of the area of the sheath part to thearea of the superconductor filament part in the cross section of asuperconducting wire) of 2.2. Next, the obtained superconducting wire 1was divided into five pieces to examine a variation in a criticalcurrent value (A) of each piece of superconducting wire 1. Table 1 showsthe results.

TABLE 1 Variation in Critical Sample No. Current Value Thickness afterthe First Sintering 1  8 A No Change 2 10 A No Change 3 30 A Thicknesswas increased at both end portions

As shown in Table 1, as for sample 1 in which sealing was performedafter the first drawing, the variation in the critical current value was8 A, and as for sample 2 in which sealing was performed after the 20thdrawing, the variation in the critical current value was 10 A. Incontrast, as for sample 3 in which the both end portions were notsealed, the variation in the critical current value was 30 A. Further,although no change was observed in the thickness of samples 1 and 2after the first sintering (Step S9), the thickness of sample 3 wasincreased at the both end portions. From the results obtained above, ithas been found that sealing the both end portions of multifilamentarywire 1 c in the interval between the step of drawing (Step S6) and thestep of the first rolling (Step S8) allows the wire to have a uniformthickness, and thus a superconducting wire with high and uniformperformance can be obtained. In particular, it has been found that, whena plurality of drawing are performed, a superconducting wire havingfurther uniform performance can be obtained by sealing the wire at astage as early as possible (at a stage where the wire is thick).

It should be understood that the embodiment and the examples hereindisclosed are by way of illustration in all respects and not to be takenby way of limitation. The scope of the present invention is defined notby the above description but by the appended claims, and is intended toinclude all the modifications within the meaning and the scopeequivalent to those of the claims.

1. A method of manufacturing a superconducting wire, comprising: drawinga wire formed by coating raw material powder for a superconductor with ametal, the wire being one of a monofilamentary wire and amultifilamentary wire, said wire being drawn n times (n is an integersatisfying n≧2), rolling said wire after said step of drawing said wiren times, and sealing an end portion of said wire in an interval betweenthe step of k^(th) (k is an integer satisfying n−1≧k≧1) drawing in saidstep of drawing said wire n times and the step of(k+1)^(th) drawing insaid step of drawing said wire n times, and maintaining said seal duringthe drawing.
 2. The method of manufacturing a superconducting wireaccording to claim 1, wherein said end portion of said wire is sealedwith a metal in said step of sealing.
 3. The method of manufacturing asuperconducting wire according to claim 2, wherein said metal containsat least one element selected from the group consisting of silver, lead,tin, copper, and aluminum.
 4. The method of manufacturing asuperconducting wire according to claim 1, sealing further comprisesproviding a sealing member configured to encase the end portion of thewire.
 5. The method of manufacturing a superconducting wire according toclaim 4, wherein the sealing member comprises caps made of Teflon. 6.The method of manufacturing a superconducting wire according to claim 1,wherein the wire is formed in a cylindrical shape having a lengthwisedimension and a base, and wherein sealing an end portion comprisescovering the base and at least a portion of the height.
 7. The method ofmanufacturing a superconducting wire according to claim 1, whereindrawing and sealing comprise alternating a drawing step with a sealingstep, a plurality of times.
 8. The method of manufacturing asuperconducting wire according to claim 1, sealing comprises a firstsealing step occurring after drawing the wire one of the n times andbefore drawing the wire another one of the n times.
 9. The method ofmanufacturing a superconducting wire according to claim 8, sealingfurther comprises a further sealing step occurring after the another oneof the n times of drawing and drawing comprises a further drawing of thewire after the further step of sealing.
 10. The method of manufacturinga superconducting wire according to claim 1, sealing further comprisingsealing the end portion of said wire during each interval between thestep of k^(th) (k is an integer satisfying n−1≧k≧1) drawing in said stepof drawing said wire n times and the step of (k+1)^(th) drawing in saidstep of drawing said wire n times.
 11. The method of manufacturing asuperconducting wire according to claim 1, sealing further comprisingsealing the end portions of the multifilamentary wire.